1. Field of the Invention
The present invention relates to a space photovoltaic power generation system for receiving sunlight in space so as to generate electric power, for transmitting the electric power to an electric power base via space by converting the electric power to a microwave, and for storing the electric power in the electric power base so as to allow the use of the electric power, and a power satellite and an electric power base for use with the system.
2. Description of the Prior Art
A solar cell is known as a small-size power generation system which utilizes sunlight. Furthermore, a photovoltaic power generation panel or the like, which can be set up on a building, is known as a power generation system intended for the home which utilizes sunlight. Such a photovoltaic power generation system built on the earth is not necessarily efficient fundamentally because of the attenuation of sunlight in the earth""s atmosphere and the alternation between shade and light caused by the alternation between day and night. A solar panel, which can be installed in a satellite, is known as a photovoltaic power generation device intended for space. Satellites can thus achieve missions by privately generating necessary electric power for observation and communications, etc. by using a solar panel. In either of the prior art power generation systems, specific equipment connected to the solar cell by cable is adapted to use the energy generated by the solar cell.
On the other hand, as the communication technology progresses according to results of recent space development works and the construction technology to construct a large-scale space structure progresses, research and development of a system that receives sunlight in space, generates electric power, and transmits the generated energy to a specific place such as a specific location on the earth or in space has been actively conducted. There can be provided an example of such a space photovoltaic power generation system including a plurality of power satellites arranged in space, each of which can focus sunlight to a number of solar panels, photoelectric-convert the incident sunlight so as to generate electric power, and then generate a microwave based on the generated energy and transmit the microwave to an electric power base built on the earth. The electric power base built on the earth includes a receiving antenna for receiving incident microwaves. The electric power base converts the received microwaves into DC signals and then combines DC electric power.
To improve the power generation capability of the prior art space photovoltaic power generation system constructed as above, a large number of power satellites each for transmitting a microwave towards the ground by a transmission antenna thereof should be arranged in space. A problem is, however, that the microwaves transmitted, via the transmission antennas of the plurality of power satellites, from the plurality of power satellites interfere with one another. It can be assumed that the group of transmission antennas is a single huge phased array antenna for transmitting microwaves. A problem is, however, that as the number of power satellites is increased to improve the power generation capability of the space photovoltaic power generation system, the area of the array antenna defined as the group of transmission antennas is increased and the beam width of the microwave transmitted via the array antenna is therefore narrowed greatly, and this results in an increase in the per-unit-area electric power received on the earth.
The present invention is proposed to solve the above-mentioned problem. It is therefore an object of the present invention to provide a space photovoltaic power generation system capable of reducing the power density of electric power transmitted from a group of power-satellites each for generating electric power from sunlight received to an electric power base on the earth and hence a loss in the total amount of energy transmitted to the electric power base on the earth, and a power satellite and an electric power base for use with the system.
In accordance with an aspect of the present invention, there is provided a space photovoltaic power generation system comprising: a plurality of power satellites each for generating electrical energy from sunlight in space, for generating an incoherent microwave from the generated electrical energy, and for transmitting the incoherent microwave; and an electric power base located at a remote site for receiving a plurality of incoherent microwaves transmitted from the plurality of power satellites, and for generating electric power from the plurality of incoherent microwaves received.
In accordance with a preferred embodiment of the present invention, each of the plurality of power satellites includes a condensing and power generating unit for focusing sunlight in space and for converting the focused sunlight into electrical energy, and a transmission unit for generating a microwave based on the electrical energy from the condensing and power generating unit, for modulating the microwave so as to generate an incoherent microwave, and for transmitting the incoherent microwave to space. Each of the plurality of power satellites can include a plurality of condensing and power generating units each for focusing sunlight in space and for converting the focused sunlight into electrical energy, and a plurality of transmission units each for generating a microwave based on the electrical energy from the plurality of condensing and power generating units, for modulating the microwave so as to generate an incoherent microwave, and for transmitting the incoherent microwave to space.
In accordance with another preferred embodiment of the present invention, the electric power base includes a receiving unit for receiving the plurality of incoherent microwaves transmitted from the plurality of power satellites, a microwave-to-DC conversion unit for converting the plurality of incoherent microwaves received by the receiving unit into DC electric power, and a transmission unit for transmitting the DC electric power obtained by the microwave-to-DC conversion unit.
In accordance with another aspect of the present invention, there is provided a power satellite comprising: a condensing and power generating unit for focusing sunlight in space and for converting the focused sunlight into electrical energy; and a transmission unit for generating a microwave based on the electrical energy from the condensing and power generating unit, for modulating the microwave so as to generate an incoherent microwave, and for transmitting the incoherent microwave to space. Preferably, the power satellite can include a plurality of condensing and power generating units each for focusing sunlight in space and for converting the focused sunlight into electrical energy, and a plurality of transmission units each for generating a microwave based on the electrical energy from the plurality of condensing and power generating units, for modulating the microwave so as to generate an incoherent microwave, and for transmitting the incoherent microwave to space.
In accordance with a further aspect of the present invention, there is provided an electric power base comprising: a receiving unit for receiving a plurality of incoherent microwaves transmitted from a plurality of power satellites; a microwave-to-DC conversion unit for converting the plurality of incoherent microwaves received by the receiving unit into DC electric power; and a transmission unit for transmitting the DC electric power obtained by the microwave-to-DC conversion unit.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.